Determine the effect of treatment w/AVONEX (Interferon-beta 1 a) supplied by Biogen on symptoms of Idiopathic Pulmonary Fibrosis (IPF). Also, to determine the effect of AVONEX on breathing tests and on scars in the lungs of patients w/IPF, and to determine the safety of AVONEX in patients w/IPF. SPECIFIC AIMS: Determine whether treatment w/AVONEX, Interferon Beta 1a, can modify the clinical course of patients w/idiopathic pulmonary fibrosis.